Power button works but won't turn PC on.!??!.?

Bearded1

Junior Member
Sep 29, 2015
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0
0
Story so far....New heart for my pc a cpl weeks ago. Everything goes swimmingly. Yesterday morning, go to turn pc on and nothing. No blip of leds or fans, nothing. Pull the side off, no loose wires. pull the power switch wire off and try shorting the terminals. Still nothing. So at this stage i'm thinking PSU let the magic smoke out. Decide to pull the main 24 pin connector off and short pins 4 and 7 to see if owt happens. PSU blips, leds flash and fans all twitch. Plug connector back into mobo and pc boots straight up no problem(without touching button again). Check all the voltages in windows, everything completely within spec whether loaded or idle. Check the power button from windows(set to hibernate) and that's fine. Works fine when i turn pc back on 2 mins later. Same result later in day when i try turning off for a cpl mins. Turn it off last night when i go to bed and guess what happens first thing this morning? Same rigmorole with having to short psu pins to boot pc. I left the pc turned off this afternoon when i finished my tea break and when i tried turning on this eve, nothing again. So it seems like the pc needs to be off for a while before this happens.

I have a sneaking suspicion what the problem is but i just want to get some other opinions first.

Thanks in advance

Specs. ASUS Z97-P, 8GB Crucial DDR3, i5 4690k, 250GB Crucial BX100, Corsair 350w. All parts less than 3 weeks old.
 

Ketchup

Elite Member
Sep 1, 2002
14,545
236
106
.... Plug connector back into mobo and pc boots straight up no problem(without touching button again)....

What does this mean? Does the power button power it up from an off state or does it not?
 

Bearded1

Junior Member
Sep 29, 2015
17
0
0
Unfortunatly don't have access to another psu to test with.
The power button works.(checked with cont. tester) However if u try shorting the 2 pins that the switch connects to nothing happens. But if u directly short pins 4 and 7 on the 24 pin power supply plug(the same 2 pins the mobo power switch connector activates) it boots. And the thing with working fine if pc has recently been on but not working after a cpl hrs seems to imply something on the motherboard.

could be wrong tho. 's why i wanted other opinions.
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
It sounds like you have the problem solved.

If you short the power switch pins on the mobo front panel header, and the board doesn't power up...
 

Burpo

Diamond Member
Sep 10, 2013
4,223
473
126
Have you tried unplugging the power cord from the wall? When it won't start, unplug it for a few seconds, re-plug and try it..
 

corkyg

Elite Member | Peripherals
Super Moderator
Mar 4, 2000
27,370
238
106
I have had the same problem, and I used an easier version of what Burp'o suggests. I reach back and turn off the master PSU switch located in the back on the PSU. Then I turn it back on and the system boots normally.

BTW, in my setup, it is easier to pull the power plug from the back of the PC than from the wall. :)
 

VirtualLarry

No Lifer
Aug 25, 2001
56,331
10,043
126
I have had the same problem, and I used an easier version of what Burp'o suggests. I reach back and turn off the master PSU switch located in the back on the PSU. Then I turn it back on and the system boots normally.

BTW, in my setup, it is easier to pull the power plug from the back of the PC than from the wall. :)

If you have to do that, then you need to replace your PSU.
 

Bearded1

Junior Member
Sep 29, 2015
17
0
0
Have you tried unplugging the power cord from the wall? When it won't start, unplug it for a few seconds, re-plug and try it..

Yep tried that. Absolutely no response to either turning it straight back on or leaving it completely powered off for a bit. Leaving it on standby worked last night. Turned on as soon as i clicked mouse. Seems like as long as mobo is powered in some way it's fine.
The problem atm is i'm working 10-12 hrs a day so can't actually try some organised testing to see how long the crossover to not turning on takes. I'm off next week tho so it might take a few days to track things down.
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
CMOS battery?

I wonder if a bad cmos battery could cause that turn on circuit to fail?
 

silicon

Senior member
Nov 27, 2004
886
1
81
Unfortunatly don't have access to another psu to test with.
The power button works.(checked with cont. tester) However if u try shorting the 2 pins that the switch connects to nothing happens. But if u directly short pins 4 and 7 on the 24 pin power supply plug(the same 2 pins the mobo power switch connector activates) it boots. And the thing with working fine if pc has recently been on but not working after a cpl hrs seems to imply something on the motherboard.

could be wrong tho. 's why i wanted other opinions.

at the very least try and get another power supply to try. to me its seems like the psu could be faulty from the description of the problem.
 

corkyg

Elite Member | Peripherals
Super Moderator
Mar 4, 2000
27,370
238
106
If you have to do that, then you need to replace your PSU.

Yeah, I know that. But, there are other things going on that are more important right now. The whole system needs to be replaced, actually, and after our pending move happens, I will get around to that. :)
 

Bearded1

Junior Member
Sep 29, 2015
17
0
0
Right i think i'm on the track of it now. I also asked this question over on techreport forums and someone there mentioned checking the +5vsb while pc was off. That was fine (5.21v) but while i was inside i also checked the PS_ON# (green wire). That was only showing 4.4v while according to the ATX 2.2 spec it should be 5v. I don't know if that being low would cause the problems i've been having but it is rather suspicious.
If there's anyone who actually understands the working of power supplies could chime in that would be greatly appreciated.
 

VirtualLarry

No Lifer
Aug 25, 2001
56,331
10,043
126
Right i think i'm on the track of it now. I also asked this question over on techreport forums and someone there mentioned checking the +5vsb while pc was off. That was fine (5.21v) but while i was inside i also checked the PS_ON# (green wire). That was only showing 4.4v while according to the ATX 2.2 spec it should be 5v. I don't know if that being low would cause the problems i've been having but it is rather suspicious.
If there's anyone who actually understands the working of power supplies could chime in that would be greatly appreciated.

My friend's PC, with a 5 year old PSU, had a weird "delay" powering up. I could push the power button, and then like literally five minutes later it would power-on. I believe I correctly diagnosed that he had a problem with the +5Vsb line, and thus the power-on circuits in the mobo. I replaced the PSU, and then it powered up without problems.
 

Bearded1

Junior Member
Sep 29, 2015
17
0
0
Weel i've found it. Shut down last night as usual, got up this morning and no response again so rechecked the +5vsb and PS_ON#. +5vsb is fine but the PS_ON# which is supposed to also be showing 5v was showing 0.01v. Poxy cheap assed sh**y PSU. It's only about 3 weeks old as well. Unfortunately i'll have to put up with it for another few days before i can remove it and get it replaced.

Thanks again for your time and help ppl.